Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
Note:
The solution set must not contain duplicate triplets.
Example:
Given array nums = [-1, 0, 1, 2, -1, -4], A solution set is: [ [-1, 0, 1], [-1, -1, 2] ]
Solution in C++
class Solution { public: vector<vector<int>> threeSum(vector<int>& nums) { vector<int>n(3); set<vector<int>> sRet; vector<vector<int>> vRet; sort(nums.begin(), nums.end()); map<int,int> mNums; for(int i=0; i<nums.size(); i++) mNums[nums[i]]=i+1; for(int i=0;i<nums.size(); i++) { if (nums[i]>0) break; n[0]=nums[i]; for(int j=i+1;j<nums.size(); j++) { int sum2=0-nums[i]-nums[j]; if (sum2<nums[j]) break; n[1]=nums[j]; if (mNums[sum2] && mNums[sum2]!=(i+1) && mNums[sum2]!=(j+1)) { n[2]=sum2; sRet.insert(n); } } } for(auto s:sRet) vRet.push_back(s); return vRet; } };